DESCRIPTION: Urban TB is a persistent problem that has caused substantial morbidity and emerged as a renewed public health threat during the past several years. Studies of its transmission have been substantially enhanced by the advent of molecular methods for strain typing. These have permitted the realization, for instance, that a higher proportion of cases of TB represent recent acquisition of infection, rather than reactivation of disease. The application proposes to combine these molecular methods with geographic information systems (GIS) technology and methods to further elucidate the epidemiology of TB, and also to assess the impact of DOT on the distribution of cases. The combination of molecular TB strain genotyping and GIS approaches will be used to track microepidemics and to test the hypothesis that genetically related cases of TB occur within a more restricted geographic area than sporadic cases and are more likely to be the result of incident cases than of reactivation of latent infections, which is more likely in low prevalence areas. The outcome goal is try to understand factors that promulgate high rates of spread in areas with persistent clonal TB microepidemics and to try to develop intervention strategies.